Magnetic recording material must have excellent tape-running properties and high durability on the back side of their supports since they are often wound up and made to run at a high speed.
With the intention of improving the running properties and durability of magnetic tape, it has been proposed to provide a backing layer and to employ cellulose resins, polyurethane resins of polyester type and isocyanate compounds in combination as a binder in the backing layer (e.g., in Japanese Patent Publication No. 44489/81). Further, the examples of the binders used in a backing layer are described in U.S. Pat. Nos. 4,135,016 and 4,273,797. Such binders have a tend to improve the durability of the resulting coated layers under high temperature and high humidity conditions. However, the effects of such binders are still insufficient. In addition, under low temperature and low humidity the the resulting coated films tend to break away creating a great number of drop out spots. Therefore, such magnetic tapes are not well suited for practical use.